Generally, a server rack is provided with a plurality of fan modules for dissipating heat generated by servers mounted in the server rack.
Rotation speed of the fan modules are usually controlled by a Rack Management Controller (RMC) according to current temperature of the servers in the server rack and the demand for dissipating heat. When a malfunction of the RMC occurs or the RMC is removed for maintenance, additional circuits such as a Pulse Width Modulation (PWM) circuit may take over the role of the RMC and control the fan modules to rotate at a full speed. However, as a result of full speed rotation of the fan modules, power consumption and noise generated by the fan modules are considerably increased, and lifecycle of the fan modules may be decreased. An alternative solution is to provide an additional processor hot (prochot) circuit which may be employed as an additional circuit for controlling rotation speed of the fan modules to be at a constant speed and for reducing computing performance of the servers, e.g., adjusting operating frequencies of processors in the servers, so as to ensure that the servers operate at a safe operating temperature.